Fluid atomizers

ABSTRACT

The invention comprehends a fluid atomizer comprising an atomizer nozzle having a discharge orifice communicating with a cavity in said nozzle of convergent axial section towards said discharge orifice, and a swirler insert snugly fitted in said cavity and having an axial section complementary thereto, said swirler insert being axially spaced from said discharge orifice to define between the smaller cross sectional end of said swirler insert and said discharge orifice a swirl chamber forming part of said cavity, said swirler insert having a plurality of passages extending in and along its peripheral wall to provide for fluid flow, between the interfitting peripheral surfaces of said atomizer nozzle and said swirler insert, through said passages each of said passages extending at its discharge end adjacent said swirl chamber in a direction generally tangential of said chamber, so that fluid emerging from said discharge end will flow in an axial direction generally following the peripheral surface of said swirl chamber and tangentially thereto.

United States Patent Needham et al. [451 Sept. 19, 1972 [54] FLUID ATOMIZERS 1,436,189 3/1966 France .'.....239/488 [72] Inventors: Arthur Michael Needham, Backwell;

David Tindall, Dibden Purlieu, both of England Attorney-Lawrence E. Laubscher [73] Assignee: J. & T. Engineers (Ascot) Limited 22 Filed: Jan. 15, 1971 [57] ABSTRACT The invention comprehends a fluid atomizer compris- [211 P 106516 ing an atomizer nozzle having a discharge orifice communicating with arcavity in said nozzle of convergent 3 Foreign Application priority Data axial section towards said discharge orifice, and a swlrler insert snugly fitted III said cavity and having an Jan. 16, Great Blltall'l ection complementary thereto wifler insert being axially spaced from said discharge orifice to [52] US. Cl ..239/488, 239/494 define between the smaller cross sectional end of said [51] Int. Cl. ..B05b l/34 swirler insert and said discharge orifice a swirl [58] Field of Search ..239/46 1 463, 486, 487, 488, chamber forming p of ai i y, i swirler insert 239/489, 493, 494, 496, 497 having a plurality of passages extending in and along its peripheral wall to provide for fluid flow, between [56] Rderences Cited the interfitting peripheral surfaces of said atomizer nozzle and said swirler insert, through said passages UNITED STATES PATENTS each of said passages extending at its discharge end adjacent said swirl chamber in a direction generally 262,183 8/1882 I-Iogan ..239/487 tangential of Said chamber so that fluid g g 1,089,406 3/1914 Fittsm ..239/488 X from said discharge end will flow in an axial direction St. Clalr X the surface of said 1,731,813 BIOOITI X chamber and thereto 2,776,862 1/1957 Bloom ..239/488 X 9 Claims, 10 Drawing Figures FOREIGN PATENTS OR APPLICATIONS 1,127 5/1909 Great Britain ..239/493 Pl 7 p2 pmmsnsms I972 3,692,245

SHEET 2 0F 2 F/c. IO.

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ATTORNEY FLUID ATOMIZERS This invention concerns improvements in or relating to fluid atomizers.

According to the invention there is provided a fluid atomizer comprising an atomizer nozzle having a discharge orifice communicating with a cavity in said nozzle of convergent axial section towards said discharge orifice, and a swirler insert snugly fitted in said cavity and having an axial section complementary thereto, said swirler insert being axially spaced from said discharge orifice to define between the smaller cross-sectional end of said swirler insert and said discharge orifice a swirl chamber forming part of said cavity, said swirler insert having a plurality of passages extending in and along its peripheral wall to provide for fluid flow, between the interfitting peripheral surfaces of said atomizer nozzle and said swirler insert, through said passages, each of said passages extending at its discharge end adjacent said swirl chamber in a direction generally tangential of said chamber, so that fluid emerging from said discharge end will flow in an axial direction generally following the peripheral surface of said swirl chamber and tangentially thereto.

In order that the invention may be well understood there will now be described some embodiments thereof, given by way of example only, reference being had to the accompanying drawings, in which:

FIG. 1 is a cross sectional side elevation of a fluid atomizer assembly;

FIG. 2 is a cross sectional side elevation of an atomizer nozzle for said fluid atomizer assembly;

FIG. 3 is a side elevation of a swirler insert completing said fluid atomizer assembly;

FIG. 4 is a front elevation of the same swirler insert;

FIGS. 5, 6 and 7 are side elevations of three alternative swirler inserts, only one fluid passage being shown for ease of illustration, although it is to be understood that a plurality of such passages would be provided;

FIG. 8 is a front elevation of a further alternative swirler insert;

FIG 9 is a cross sectional side elevation of the fluid atomizer assembly, shown in FIG. I, mounted in a conventional fluid spray tube; and

FIG. 10 is a cross sectional side elevation of the fluid atomizer assembly, shown in FIG. I, mounted in a conventional fluid spray tube with provision for the return of fluid from the atomizer assembly.

The fluid atomizer assembly is primarily intended, for incorporation in an oil fuel burner suitable for use in a steam generating boiler or in any other application where the fluid has to be sprayed in the form of finely divided droplets evenly dispersed.

The fluid atomizer assembly, shown in FIGS. 1 to 4, comprises two components, the atomizer nozzle 1 and the atomizer swirler insert 2. The atomizer nozzle 1 includes a cavity In which in axial section is convergent towards a discharge orifice 10 of the nozzle. In each of the present embodiments, the cavity la is of conical configuration. The swirler insert 2 has an axial section complementary to that of the cavity la, i.e. in the particular case the swirler insert is conical, and is sized to snugly fit into larger end of the cavity la to define a swirl chamber lb between itself and the discharge orifice 10. The swirler insert 2 is normally clamped in the atomizer nozzle 1 by means of a capnut 3 and a tube 4 or by the capnut 3 and a tube 5, as shown in FIG. 9 and 10 respectively.

Fluid is delivered to the atomizer assembly under pressure by way of the tube 4 or an annular space 6 around the tube 5. Due to the swirler insert 2 being clamped in the atomizer nozzle 1, the fluid is constrained to flow between the swirler insert 2 and the atomizer nozzle 1 through passages 7 formed in the conical wall 2a of the swirler insert to run therealong and open into the swirl chamber lb tangentially thereto.

Due to the inclination of the passages 7 to the axis of the swirler insert 2, the fluid jets on leaving the constraint of the passages 7 tend to follow the conical wall 8 of the swirl chamber lb and have velocity components in both an axial and tangential direction.

In one particular swirler insert 2, shown in FIGS. 3 and 4, the cross sectional area of each of the passages 7 decreases in the direction of fluid flow due to the depth of each passage decreasing in said direction and the fluid is accelerated on passing through the passages 7.

In an alternative swirler insert 2 shown in FIG. 5, at the entrance to each of the passages 7, the axis of each passage is parallel to the axis of the swirler insert 2.

In another alternative swirler insert 2 shown in FIG. 6, the entrance to each of the passages 7 is radiused at to minimize the energy required to accelerate the flow of fluid from the tube 4 or the annular space 6 into the passages 7.

In another alternative swirler insert 2 shown in FIG. 7, the rate of change of curvature of the passages 7 is maintained constant.

In a further alternative swirler insert 2 shown in FIG. 8, each of the passages 7 decreases in width, normal to the axis of the passage, in a radially inward direction so as to reduce the cross-sectional area of each passage in the direction of fluid flow.

The fluid on leaving the constraint of the passages 7 of the swirler insert 2 is further constrained by the conical wall 8 of the atomizer nozzle 1. The circular cross sectional of the interior of the nozzle 1, normal to the axis of the nozzle, bounded by the conical wall 8, decreases, of course, in the direction of the fluid flow.

This convergence causes the fluid flow to accelerate in both axial and tangential directions in the swirl chamber lb until an edge 9 of the discharge orifice 10 of the nozzle 1 is reached. The force required for this acceleration of fluid flow is supplied by the difference in pressure between P2 and P3 as shown in FIG. 9 and FIG. 10.

The convergence of the nozzle wall 8 causes the separate fluid jets, as at the exit of the passages 7, to amalgamate in the swirl chamber lb. The fluid is emitted from the discharge orifice 10 with axial and tangential components of velocity, and on leaving the constraint of the orifice 10, the fluid forms into a conical sheet of an included angle B of uniform thickness which under the influences of various forces acting on and within the fluid, breaks into droplets.

By providing a suitable number of the passages 7 of a suitable shape and form, together with suitable sizes of discharge orifice l0 and included angles A of the nozzle wall 8, the desired characteristics of fluid flow, droplet size and spray angle B may be obtained.

The described fluid atomizer assembly is advantageous in that the desired value of axial and tangential velocity given to the fluid flow at the exit of the passages 7 is achieved with the minimum loss of energy,

resulting in more energy being available to impart further increases in axial and tangential velocity within the convergent nozzle bounded by the wall 8. For a given pressure P1 in the tube 4 or the annulus 6 and a given quantity of fluid flow, an improved spray is achieved than with conventional atomizers.

Again, because of the increased value of the pressure P2 for a given value of P1, at a given fluid flow, a greater pressure difference is available for the return of fluid from the atomizer in a system as shown in FIG. 10, thus a greater degree of control of the flow fluid to be atomized can be obtained without detriment to the quality of the atomization.

Further, since the fluid discharges into the swirl chamber lb having both axially forward and tangential components of velocity, friction due to drag on the conical wall 8 of the swirl chamber is reduced with consequential reduction in the rate of wear of that wall,

giving proper atomization for longer periods of service than is possible with conventional atomizers.

As stated, the area of each passage, in particular embodiments of swirler insert, as it approaches the swirl supply pressure Pl, so that by altering the length of the swirler insert 2, the discharge area of the passages 7 is varied, and thus the flow through the discharge orifice for a given value of the supply pressure P1.

The various constructional features of the different embodiments may be combined where appropriate.

What we claim is: l. A fluid atomizer, comprising a. an atomizer nozzle having a discharge orifice communicating with a cavity in said nozzle of convergent axial section towards said discharge orifice;

. a swirler insert snugly fitted in said cavity and having an axial section complementary thereto, said swirler insert being axially spaced from said discharge orifice to define between the smaller cross sectional end of said swirler insert and said discharge orifice a swirl chamber forming part of said cavity, said swirler insert having a plurality of passages extending in and along its peripheral wall toprovide for fluid flow between the interfitting peripheral surfaces of said atomizer nozzle and said swirler insert, and through said passages, each of said passages extending at its discharge end adjacent said swirl chamber in a direction generally tangential of said chamber, so that fluid emerging from said discharge end will flow in an axial direction generally following the peripheral surface of said swirl chamber and tangentially thereto; c. and means clamping said swirler insert within said atomizer nozzle, said clamping means including 1. flow tube means externally threaded at one end;

and 2. a capnut threadably connected with said flow tube means and in engagement with said atomizer nozzle to clamp said atomizer nozzle and said swirler insert against one end of said flow tube means. 2. A fluid atomizer is claimed in claim 1, wherein said cavity is of conical configuration and said swirler conical.

ins rt i al 3 Ailui atomlzer as claimed in claim 2, wherein the cross sectional area of each of said passages decreases towards said discharge end thereof.

4. A fluid atomizer as claimed in claim 3, wherein each of said passages decreases in width towards said discharge end thereof.

5. A fluid atomizer as claimed in claim 3, wherein each of said passages decreases in depth towards said discharge end thereof.

6. A fluid atomizer as claimed in claim 1, wherein each of said passages at its inlet end extends in a direction parallel to the axis of said swirler insert.

7. A fluid atomizer as claimed in claim 1, wherein each of said passages is curved and the rate of change of curvature thereof is constant through the length of the passage.

8. A fluid atomizer as claimed in claim 1, wherein each of said passages at its inlet end is radiused.

9. Apparatus as defined in claim 1, wherein said swirler insert contains a central axial passage, and further wherein said flow tube means includes a pair of concentrically spaced inner and outer flow tubes that define therebetween a flow path to the inlet end of each of said passages, said inner flow tube defining therein a flow path from said swirl chamber via said central axial passage. 

1. A fluid atomizer, comprising a. an atomizer nozzle having a discharge orifice communicating with a cavity in said nozzle of convergent axial section towards said discharge orifice; b. a swirler insert snugly fitted in said cavity and having an axial section complementary thereto, said swirler insert being axially spaced from said discharge orifice to define between the smaller cross sectional end of said swirler insert and said discharge orifice a swirl chamber forming part of said cavity, said swirler insert having a plurality of passages extending in and along its peripheral wall to provide for fluid flow between the interfitting peripheral surfaces of said atomizer nozzle and said swirler insert, and through said passages, each of said passages extending at its discharge end adjacent said swirl chamber in a direction generally tangential of said chamber, so that fluid emerging from said discharge end will flow in an axial direction generally following the peripheral surface of said swirl chamber and tangentially thereto; c. and means clamping said swirler insert within said atomizer nozzle, said clamping means including
 1. flow tube means externally threaded at one end; and
 2. a capnut threadably connected with said flow tube means and in engagement with said atomizer nozzle to clamp said atomizer nozzle and said swirler insert against one end of said flow tube means.
 2. a capnut threadably connected with said flow tube means and in engagement with said atomizer nozzle to clamp said atomizer nozzle and said swirler insert against one end of said flow tube means.
 2. A fluid atomizer is claimed in claim 1, wherein said cavity is of conical configuration and said swirler insert is also conical.
 3. A fluid atomizer as claimed in claim 2, wherein the cross sectional area of each of said passages decreases towards said discharge end thereof.
 4. A fluid atomizer as claimed in claim 3, wherein each of said passages decreases in width towards said discharge end thereof.
 5. A fluid atomizer as claimed in claim 3, wherein each of said passages decreases in depth towards said discharge end thereof.
 6. A fluid atomizer as claimed in claim 1, wherein each of said passages at its inlet end extends in a direction parallel to the axis of said swirler insert.
 7. A fluid atomizer as claimed in claim 1, wherein each of said passages is curved and the rate of change of curvature thereof is constant through the length of the passage.
 8. A fluid atomizer as claimed in claim 1, wherein each of said passages at its inlet end is radiused.
 9. Apparatus as defined in claim 1, wherein said swirler insert contains a central axial passage, and further wherein said flow tube means includes a pair of concentrically spaced inner and outer flow tubes that define therebetween a flow path to the inlet end of each of said passages, said inner flow tube defining therein a flow path from said swirl chamber via said central axial passage. 